How many % of software is domain modeled? Must me a small minority.

Nearly 100%. They don't call it that or use that term, and almost never _design_ thinking about the domain. But the absence of a formal 'domain model' still results in domain modeling - it's just done at the level of IC who may or may not have any awareness of the broader implications of the model they are creating.

I’d say all (useful) software is modelling some domain.

Plenty if developed under consulting contract.